A HERDSMAN'S HANDBOOK FOR THE MODERN HOMESTEADER

Article Tools

Image Gallery

Print

E-mail

Comments

RSS

» TAPE WORMS

Tapeworms—flat, segmented, ribbon-like creatures that may be three-quarters of an inch wide and several feet long-are rather more complicated than roundworms. Tapeworm species whose adult stages are present in the ruminant— Moniezia expansa and M. benedeni —do relatively little damage to mature animals and cases of symptomatic disease caused by them occur only occasionally in sheep and in calves.

The head of the adult tapeworm attaches to the lining of the intestine and each segment of the creature is a separate reproductive unit. As they mature, the terminal segments—full of eggs—break off from the main body and are expelled by the host with its feces. The eggs next must be eaten by a free-living orabatid mite that frequents most moist pasture areas. Larval development takes place within the mite and, if the infected mite is then consumed by a ruminant, the larvae mature in the gut of the new host and the process begins anew.

The adult stages of two additional tapeworms— Taenia echinococcus and T. hydatigena —occur in dogs, wolves, and other members of the canine family rather than in ruminants, Cattle, however, do become infected with the parasites by ingesting the eggs in feed or water that has been contaminated with the feces of infected dogs.

The larvae then penetrate the afflicted cow's gut wall and are carried by its blood stream to selected sites in the body organs or muscles, where they form cysts. These cystic stages—called Echinococcus granulosus and Cysticercus tenuicollis —take the form of fluid-filled sacs up to one inch in diameter. A common name for the sacs is hydatid cysts . . . and they may or may not cause symptoms, depending on their location in the body. A canine becomes the new host for Taenia echinococcus and T. hydatigena by eating tissues containing these cysts.

The so-called "beef tapeworm of man" ( T. saginata) has a similar life cycle involving cattle and people. Cattle are subjected to T. saginata cystic infection after exposure to the tapeworm's eggs in feed or water contaminated with feces from people who have consumed the cysts in improperly cooked meat.

The widespread use of flush-toilets has practically eliminated this parasite, but it is possible that it could again become a problem in some rural settings where human wastes are not disposed of properly.

» FLATWORMS OR FLUKES

Only three kinds of liver flukes occur in the continental United States. Fascioloides magna is a natural parasite of deer, elk and moose in many of the states bordering Canada. Dicrocoelium dendriticum, the lancet fluke, occurs only in a small area in central New York State. The common liver fluke (Fasciola hepatica) is found in the Southeast, the Gulf Coast, parts of the Southwest, the Rocky Mountain region and the Pacific Coast states . . . where it has been found to infect deer, cattle, sheep, goats, rabbits, swine, horses and humans.

RSS | Comments | E-mail | Print